Silicon wafers grown by the Czochralski (CZ) method, e.g. by the standard CZ method or by the magnetic CZ (MCZ) method or by the Continuous CZ (CCZ) method serve as a base material for manufacturing a variety of semiconductor devices and integrated circuits such as power semiconductor devices and solar cells. In the Czochralski method, silicon is heated in a crucible to the melting point of silicon at around 1416° C. to produce a melt of silicon. A small silicon seed crystal is brought in contact with the melt. Molten silicon freezes on the silicon seed crystal. By slowly pulling the silicon seed crystal away from the melt, a crystalline silicon ingot is grown with a diameter in the range of one or several 100 mm and a length in the range of a meter or more. In the MCZ method, additionally an external magnetic field is applied to reduce an oxygen contamination level.
Growing of silicon with defined doping by the Czochralski method is complicated by segregation effects. The segregation coefficient of a dopant material characterizes the relation between the concentration of the dopant material in the growing crystal and that of the melt. Typically, dopant materials have segregation coefficients lower than one meaning that the solubility of the dopant material in the melt is larger than in the solid. This typically leads to an increase of doping concentration in the ingot with increasing distance from the seed crystal.
Since in Czochralski grown silicon ingots, depending upon application of the grown silicon, a tolerance range of doping concentration or specific resistance along the axial direction between opposite ends of the silicon ingot may be smaller than the variability of doping concentration or specific resistance caused by segregation effects during CZ growth, it is desirable to provide a method of manufacturing a silicon ingot grown by the Czochralski method that allows for an improved axial homogeneity of specific resistance.